Combustion heater



Nov. 6, 1945.

G. A. PAGE, JR., EI'AL cmsusnon HEATER Filed Nov. 12, 1941 3 Sheets-Sheet 1 EX IAWTBZOWEP OIL PUMP 'f l 16 HA PAGE A 533E913 m 51 /535 kug aZdPH/UPR WA sorv ATTORNEY Nov. 6, 1945. s. AQPAGE. JR., ETAL 5 COMBUSTION HEATER Filed Nov. 12. 1941 s Sheets-Sheet s K '7 L19 I ATTORNEY Patented Nov. 6, 1945 cormus'rron nears-a George A. Page, In, Creve Coenr; Joseph Jerger, and Raymond Rugge, Ferguson, and Philip R. Watson, Webster Groves, Mo assignors to Ourtiss-Wright Corporation, a corporation of Delaware Application November 12, 1941, Serial No. 418,696

Claims. (01. ice-11o) I This invention relates to heating apparatus and is particularly concerned with improvements in combustion heaters of the type in which liquid fuel is mixed with air and burned in a combustion chamber, the products of combustion passing through a heat exchanger wherein ventilating air passing over the heat exchanger is warmed.

An object of the invention is to provide a combustion heater system adapted for use in vehicles and particularly adapted foruse in aircraft, the apparatus being provided with control equipment of such character as to make the apparatus safe, and substantially automatic in operation. A further object of the invention is to provide a combustion heater system so organized as to eliminate any possibility of leakage or diffusion of combustion products into the vehicle cabin. Still another object of the invention is to provide automatic safety devices which shall stop the operation of the heater apparatus in response to excessive temperature conditions in the system or malfunctioning of any of the combustion air enters the carburetor at It while liquid fuel enters same through a pipe l5. Ignition is provided for the mixture by spark plugs I 6 and as the burned mixture passes through the heat exchanger Ill, it gives up its heat to ventilating air which passes through the box II, this ventilating air being furnished under forced draft by a, ventilating blower I! or by natural means such as dynamic pressure of air due to flight velocity. Products of combustion are withdrawn from the heat exchanger through a pipe 18 and an exhaust blower IS, the exhaust pipe It being provided with an air cleaner to minimize the deposits of carbon and solid matter which might otherwise accumulate in the exhaust blower l9. Said blower I9 is provided with an Oil pump 2| whose purpose will becomeapparent shortly.

ponents of the system. Still another object of the invention is to provide a combustion heater apparatus which is adapted for use in high altitude aircraft; a particular requirement for this service is that the heater system be capable of proper functioning at atmospheric pressure much less than atmospheric pressures encountered at ground level.

Further objects of the invention will become apparent in reading the annexed detailed description in connection with the drawings, in which:

' Fig. 1 is a wiring-diagram of one arrangement of the heater system;

Fig. 2 is a mechanical diagram showing the heater system of Fig. 1;-

Fig. 3 is a wiring diagram of a second combustion heater system;

Fig. 4 is a mechanical diagram of the apparatus of the second embodiment;

i Fig. 5 is a wiring diagram of a third embodiment of the heater system;

Fig. 6 is a mechanical diagram of the apparatus of the third embodiment; and

Between the carburetor l3 and the combustion chamber l2 a fire screen 22 is disposed to prevent -backfire from the combustion chamber toward the carburetor, and a restriction is placed between the combustion chamber and the ,heat

exchanger to improve combustion.

In the usual heat transfer core involving air or any other gases in contact with both sides of the apparatus (e. g.in-tercooler) it is customary to employ only primary surfaces in the interest of heat transfer efliciency. This is done by using a large number of small diameter tubes, resulting in large primary surface. In the case of our combustionheater, the heat transfer core is constructed with relatively few and large tubes which have a large secondary surface in the form of fins. Heat transfer into the tube wall on the inside (hot) surface is limited by thesurface coeflicient Fig. 1 shows the control system for the apparatus in Fig. 2 and this will now be explained in detail: .Power is provided for the system from: a battery or the'like 30 grounded at one terminal and connected atits positive terminal through a fuse 3| to a master switch 32 and a normally closed,-stop" push button switch 33. Theme,

power iscarried to a start and run switch 34 adapted for momentary contact in either the start or run positions. For starting, after closure of the switch 32, the switch 34 is moved to the start" position which energizes a normally open relay 35. closing the main power circuit from the battery through a wire 36, the switch 35 of the relay 35, through a starting resistance 38, through the coil of a normally closed motor overload relay 31 to the motor 26. From the resistanc 38, ower i carried through fuses to the motor 25 and to an ignition system designated in its entirety as 39. Thus, the motors and ignition system start running. Simultaneously, upon closure of the start switch 34, power is carried through wires 40 and 4| to the fuel pump motor 28 startin operation thereof. Also, through a wire 42, a delay drop-out, normally open relay 43 is energized, the return circuit thereof being made through a wire 44 passing to the normally closed switch 31' of the motor overload relay 31 and thence through normall closed thermostatically controlled switches 45, 46 and 41 to ground. Energizing of the relay 43 closes the switch 43"thereof which sets up a circuit to the solenoid of a relay 49. The switch 34 is held in the start position until the exhaust blower motor accelerates to a R. P. M. which will permit application of full voltage. The

switch 34 is then quickly pushed to the run position. This completes the circuit to the sole-- nOid of relay 49 through the switch 43'. (Relay 43 was de-energized momentarily while switch 34 was being thrown over to the "run position, but owin to its time-delay drop-out, it kept switch 43' closed.) Energizing the solenoid of relay 49 closes switches 49' and 49". Switch 49" shunts the starting resistance 38, thus applying full voltage to the motors 25 and 26, and to the ignition circuit 39. The switch 49' remakes the circuit to the solenoid of relay 43, which was interrupted when switch 34 was pushed to run." Notice that the solenoid of relay 49 still gets its power through one pole of switch 34. The switch 34 is held in the run position until an indicating light 52 goes out which signifies that the oil pump 25 has begun to deliver pressure, the pressure outlet of the latter being connected through a pipe 53 to a hydraulic motor 54 which when subject to pressure, opens a switch 54' opening the power circuit to the light 52 and closing a switch 54" which leads power from the wire 40 to the solenoid of the relay 49, shunting the switch 34. Thus, as soon as the light 52 goes out, the switch 34 may be opened and operation of the system continues. Opening of the run switch before oil pressure comes on will cause the system to stop.

When it is desired to stop the heater deliberately, the stop push button switch 33 is opened, thereby cutting off power supply to the several relays, particularly the relay 49 whose switch 49" opens to stop operation of the blowers. Also, power is stopped to the fuel pump motor 28 and to the ignition system 39.

Should a short-circuit occur in motor 26, or some abnormal mechanical load be imposed on motor 26, the overload relay 31 will pick up, thereby opening the switch 31 and cutting off control power to the relay system. The motor overload relay, when picked up, engages a hook 55 which may only be disengaged by the operation of a reset solenoid 51 selectively operated by a reset switch 58.

As mentioned heretofore, the control return wire 44 is serially connected with thermostatic ed to open should airflow reverse in the ventilating duct and should its temperature reach 150 F. The thermostat of the switch 41 is disposed in the heater exhaust duct in the vicinity of the blower l9 and is adjusted toopen when combustion products at that point reach 200 F. Opening Of any one of the switches 45, 46 Or 41 opens the relay system and stops operation of the heater until the affected thermostat cools off, and the systemis voluntarily started again by the operator through manipulation of the switch 34.

The ignition system 39, provided with power at the same time as the motors .25 and 26 are provided with power, includes an igniter cut-off thermostat 60 whose control element is located in the exhaust line from the heater. As soon as ignition of the fuel-air mixture takes place, the hot exhaust gas will cause the thermostat 60 to open it normally closed contact, breaking the circuit to the ignition system and extinguishing a tel-light 6|, thus notifying the pilot that the igniter has shut off. If for some reason ignition of the fuel-air mixture does not take place, the light will remain on indefinitely thus indicating to the pilot that some part of the equipment is out of order and that the motor system should be shut down. The ignition system 39 is dual and, in the scheme shown, includes two similar coil and breaker systems, each comprising a resistor 62, a spark coil 63, and a make and break buzzer 64, intermittent high voltage from the coil 63 providing sparking current to the spark plug 16. For certain operating requirements, the spark coil system shown may be replaced with an alternating current transformer system shown in Fig. '7. This would bebetter for high altitude 7' operation. In Fig. '1, the thermostat 60 connects to a relay I20 whose switch closes an A. C. circuit energizing transformer I21, the high voltage terminals of which connect to the spark plugs.

In general, there are seven protective devices which will shut down the heater if trouble develops. These are '(a) the overload relay 31 which operates if the exhaust blower motor begins to draw excessive current, (b) the reverse flow protective thermostat 46 which opens if the heater is running when no ventilating air is flowing, (c) the normal flow protective thermostat 45 which opens if the ventilating air reaches a dangerous temperature, (d) the heater exhaust thermostat 41 which opens if the exhaust gases reach a temperature which might damage the blower. Operation of any one of these devices de-energizes the relay '49, stopping the system. (e) Protection in case of failure of oil supply to the exhaust blower bearings isprovided by the oil pressure switch 54. Should oil pressure fall to about one-half pound per square inch (p. s. i.) this switch interrupts the power to the relay 49 and at the same time the indicating light 52 comes on showing that oil pressure is low. (f) A short circuit in the motors 26 or 25 will blow their branch fuses 61 or B8, or a fuse B6 in the power line 36, (g) ,the fuse 3| will blow in case of a short circuit in any part of the control circuit system. Branch protection is provided for the ignition system by fuse 69, and for the fuel pump motor by fuse in the lead 4 I.

Now referring briefly to the embodiments of Figs. 3-4 and Figs. 5-6, both of these embodiments utilize a small gasoline engine ID for providing power for the blowers I1 and I9. Both utilize a small electric motor driven fuel pump II whose motor is indicated'at I2. The engine is provided with magneto ignition, the magneto being indicated at IS. The magneto is normally ready to operate as soon [as the engine is started, and stoppage of the engine is afforded by grounding the magneto-specifically, by short circuiting the magneto breaker. stoppage control for both the arrangements in Fig. 3 and Fig. 5, as will become apparent, hinges on grounding of the engine magneto I3.

Now referring to Figs. 3,and 4, this system includes provision for electric starting of the engine III in the form of a starting motor 14. Power to the control system is provided from a battery other terminal of which is connected through a fuse I5 and a master switch I6 to a power bus I1. From this bus power is led to the arms of a dpdt switch I8 which may be moved as indicated to start or run positions with spring return from either position. When the switch is moved to the start position, power flows from the bus 11, to the solenoid of a relay I9 whose other terminal is grounded. The relay I9 when energized, opens its normally closed switch 19'. Switch I9 is specifically to render relay 62, the shut down and lockout relay inoperative during the starting period. The other pole of the dpdt switch I8 energizes the solenoid of a relay 80, closingits switch 80' to provide power to the starting motor I4. When the'switch I6 was closed, power was also connected to a bus 8| running to the'motor 1'2 and. to the ignition system 39 through the normally closed switch 82" which served to start the fuel pump motor and the ignition system before the engine I0 was started. The relay 82 also carries a normally open switch 82 connected on one side to ground and at its other side to the.

tective device operates. Said wire 83 is also con nected to a normally closed switch 84' of a relay 84. Swith 84? grounds the magneto I3 when the heater is not being used, 1. e., when the switch 16 is open. As soon as switch I6 is closed, relay 16 picks up andremoves this particular ground fromthe magneto I3. The engine can then be started.

Movement of the dpdt starting and running switch 18 to the "run position merely disconnects the starting motor I4 from powersupply. through the relay 80 but allows continued energization of the relay 19 thereby holding the switch I9 open. A hydraulic motor86 is connected to the oil-pump H on the exhaust blower I9 and this, when provided with hydraulic pressure, opens switches 86' and 86", the latter opening the power circuit from the bus TI to a tel-light 81. The switch 86"when opened prevents'grounding of the solenoid of the relay 62 through wires 88, 89, 90, the switch I9, and the wires 9I and 92 during normal operation when the switch 19' is closed due to de-energizapage of the system may also be aiforded by closure of any one of three normally open thermostat switches 96, 91 or 98. Thermostats 96 and 91 are in the ventilating air duct and provide respectively for reverse flow protection and normal flow protection at excessive temperatures,

while the thermostat 96 is disposed in the exhaust 36 one terminal of which is grounded and the.-

haust gas temperature become too high. After the relay 82 is operated, the system may not be started again until the starting and running switch 18 is operated, as above described.

The starting motor I4 when driven by the gasoline engine 'I0may be used as a standby generating plant for the vehicle. To this end, power leads I I0 and. I I I are taken from the starter wires and led through a switch I I2 and a fuse II 3 to any other apparatusassociated with the heater system or the vehicle. By appropriate switching, the starting motor 14 acting as a generator may be used to recharge the battery 30 or to provide electrical energy for operating the fuel pump.

Now referring to Figs. 5 and 6, these showings represent a system substantially the same as that in Figs. 3 and 4 except that the engine 10 is not provided with an electric starter but rather, is provided with hand cranking provisions as shown at I00 in Fig. 6. In this system, a main power switch MI is first closed which energizes the coil of relay 8, opening the switch 84' and ungrounding the magneto I3. It also provides power to the switch 86" which at this time is closed due to lack of oil pressure in the cylinder 86 since the oil pump 2I is not yet operating. Power is also J provided to the coil of the relay 82 and to the normally closed contact 82" of said relay. The circuit to the solenoid of the relay 82 is completed through the normally closed starting switch I02 and through the switch 96' of the oil pressure switch 86 to ground. The engine I0 may not be started until the spring-return starting switch I02 is opened and held opento de-energize the relay 82, thereby ungrounding the magneto through the switch 82' and allowing the fuel pump motor I2 .and the ignition system to start operating tion of the solenoid of the relay I9. Now, should through closure of the relay switch 82". Upon motor starting and development of oil pressure in the switch 86, the tel-light 81 will go out and the switch 96' will open, cutting off power to the relay solenoid82 after which the starting switch I02 may be allowed to close. Now, the system will run so long as normal conditions prevail. Closure of any one of the protective thermostats 96, 91 or 98 will energize the relay 82 to cut oii power to the fuel pump and ignition system at the switch 82" and to ground the magneto through the switch 92. Failure of oil pressure in the unit 86 would also energize the solenoid of the relay 82. Closure of the normally open, spring return stop switch I03 accomplishes the same result. Upon temporary closure of any one of these switches the relay 82 stays in the picked up condition through grounding of its solenoid to a wire I05 leading to the switch 82" of the relay 92. Thus, starting of the system may not again be accomplished until the starting switch I02 is opened.

Regarding the oil pump 2I driven by the blower I9, a diaphragm valve is connected, by means of operation of the exhaust blower.

tubing, to the suction side of the blower and also to the discharge side of the oil pump. Said valve has incorporated a capillary restriction. As the blower is operated (starting with zero rotational speed) suction is developed at its inlet. This suction draws air from the discharge side of the centrifugal oil pump 2 I, through the capillary re striction and into the blower inlet, "causing a suction in the entire pipe and also in the oil pump and in the pipe connecting the oil pump with'its reservoir. Oil is therefore drawn through the oil pump and up to the capillary restriction which resists the flow of oil strongly enough to allow the oil pressure to come up to its full value. The oil pressure then acts upon the diaphragm closing the capillary restriction and shutting off the possible oil leakage which would otherwise take place through this opening.

In summarizing, all three of the combustion heater systems shown are extremely flexible in operation. They are inherently safe from noxious fumes in a vehicle and thecontrol and protective devices therein prevent the-possibility of continued operation of any component if any other component should fail. Particular attention is called to the manner in which the operation of the heater system is maintained by oil pressure which is, itself, maintained by proper The use of indicating lights enables the operating crew to know at-all times the condition of operation of the heater system. Any degree of automatic starting of the heater may be carried out through the use of well known electrical and thermostatic devices, whereby, in a vehicle, temperature regulation within narrow limits may be secured. Further advantages of the invention include a quick response to calls for more or less heat. The apparatus utilizes fuel from the normal vehicle fuel supply. However, the apparatus is independent of the vehicle power plant in other respects. The apparatus may be adapted for a wide range of heat capacity according to heat demand which may arise and the whole system may be arranged for low aggregate weight and small bulk to make it suitable for aircraft use.

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. We aim in the appended claims to cover all such modifications and changes.

We claim as our invention:

1. In a heating system, heating means having a combustion chamber, means for feeding fuel to said combustion chamber, means for circulating air in heat exchange relation with said heating means, an induced-draft exhaust blower for withdrawing the combustion gases from said heating means, an oil pump for supplying lubricating oil to one or more bearings of said exhaust blower, and means responsive to failure of the oil pressure delivered by said pump for stopping sai exhaust blower and fuel feeding means.

2.. In a. heating system, heating means having a combustion chamber, means for feeding fuel to said combustion chamber, means for circulating air in heatv exchange relation with said heating means, an induced-draft exhaust blower for withdrawing the combustion gases from said heating means, an oil pump for supplying lubricating oil to one or more bearings of said exhaust blower, and means responsive to failure of the oil pressure delivered by said pump for stopping said exhaust blower, fuel feeding means and air circulating means.

3. In a heating system for a vehicle propelled by an internal combustion engine, heating means having a combustion chamber, means for feeding fuel to'said combustion chamber, an induceddraft exhaust blower for withdrawing the combustion' gases from said heating means, a blower for circulating air in heat exchange relation with said heating means, an auxiliary internal combustion engine for driving both said blowers, an oil pump for supplying lubricating oil to one or more bearingsof said exhaust blower, and means responsive to failure of the oil pressure delivered by said pump for stopping said auxiliar internal combustion engine and fuel feeding means,

4. In a heating system, heating means having a combustion chamber, means for feeding fuel 'to said combustionchamber, an induced-draft exhaust blower for withdrawing the combustion gases from said heating means, a duct surrounding said heating means, means for circulating air through said duct in heat exchange relation with said heating means, and means for automatically. stopping said exhaust blower, fuel feeding means, and air circulating means when the temperature of the combustion gases becomes excessive,

5. In a heating system for a vehicle propelled by an internal combustion engine, heating means having a combustion chamber, means for feeding fuel to said combustion chamber, an induceddraft exhaust blower for withdrawing the combustion gases from said combustion chamber, a blower for circulating air in heat exchange relation with said heating means, an auxiliary internal combustion engine for driving both said blowers, and means for automatically stopping said auxiliary internal combustion engine and said fuel feeding means when the temperature of the combustion gases. becomes excessive.

GEORGE A. PAGE, JR. JOSEPH 'JERGER. RAYMOND RUGGE. PHILIP R. WATSON. 

